Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J103/00—Adhesives based on starch, amylose or amylopectin or on their derivatives or degradation products
  • C09J103/02—Starch; Degradation products thereof, e.g. dextrin
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
  • C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
  • C08L2666/54—Inorganic substances
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24628—Nonplanar uniform thickness material
  • Y10T428/24669—Aligned or parallel nonplanarities
  • Y10T428/24694—Parallel corrugations

Definitions

• the invention relates to a starch based adhesive composition that can be used to form corrugated board. More particularly the invention relates to a starch based adhesive that rapidly increases in viscosity to form high strength green bonds under conditions of heat and pressure resulting in increased manufacturing rates of corrugated board.
• Corrugated paper board or liner board is commonly prepared by first forming a corrugated element or medium by passing a cellulosic sheet between corrugating rolls forming a substantially sinusoidal or serpentine cross-section in the sheet.
• An adhesive is commonly applied to the tips of the thus formed sinusoidal portion called flutes and a noncorrugated or planar cellulosic liner is applied against the adhesive coated flutes of the corrugated elements as the corrugated sheet passes between a corrugating roll and a pressure roll.
• the resulting paper product having the corrugating medium on one side and the planar liner on another side is called a single-faced element.
• the single-faced element may be used as is in certain applications as a liner or buffer material within a container.
• More commonly adhesive is applied to the flute tips of the single-faced element and a second liner sheet is subsequently applied to the adhesive liner in a "double facer” operation.
• the second liner sheet is exposed to conditions of heat and pressure during its contact with the adhesive.
• a so-called "hot-plate” dryer section a continuously moving belt with a hot-plate or platen surface is used to partially remove water from the adhesive bond line and establish a cured adhesive bond at elevated temperatures such as 300°-400° F.
• the adhesives which have been developed to form the corrugated board or paper board are generally starch base adhesives.
• This adhesive is a carrier adhesive, wherein a portion of the starch forms a carrier gelatinized phase and the balance of the starch forms an ungelatinized phase.
• the addition of the controlled amounts of a specific soluble polyvinyl alcohol was found to substantially increase green bond strength and rate of manufacture of the corrugated board.
• the amounts of the soluble polyvinyl alcohol that can be used is limited by the fact that at higher concentrations than claimed the soluble polyvinyl alcohols tend to form the gels recognized in Czerwin and Imoto. Further, soluble polyvinyl alcohol tends not to provide any substantial water resistance to the glue line since the polyvinyl alcohol composition is stable.
• the speed at which corrugating machines can be run is limited by the rapidity of viscosity increase in the bond line between the liner and corrugated medium.
• a "green bond” is formed which holds the components together until the adhesive system forms the final heat-cured corrugated bond.
• the green bond relies solely on the viscosity of the product to maintain the integrity of the product during curing.
• polyvinyl alcohol compositions can be controlled by carefully controlling the amount of polyvinyl alcohol in relation to boric acid in the final adhesive composition and by selecting a fully hydrolyzed polyvinyl alcohol composition of appropriate molecular weight. Further a selection of a preferred lower molecular weight polyvinyl alcohol can improve the compatibility of the adhesive and the polyvinyl alcohol.
• the rate of green bond formation is increased by the presence of the alcohol, but is not limited by the rate of dissolution of a solid polyvinyl alcohol. Since green bond formation is increased corrugating machine speeds can be increased proportionately. Still further, we have found that the fully hydrolyzed polyvinyl alcohol adds to the water resistance of the corrugated board since the polymer is water insoluble at typical use temperatures.
• the novel water-resistant corrugated board adhesives of this invention are prepared by forming an aqueous emulsion, having an alkaline pH containing a solubilized fully hydrolyzed PVOH, starch, a strong alkali metal hydroxide base and a boric acid compound and optionally a basically reacting crosslinking resin, and wax.
• the corrugated paper board adhesive of this invention is preferably formed from a suspension of starch particles in water. The viscosity and solids content are important factors influencing the speed with which the paper board machine can be operated and also effects the quality of the finished paper board.
• the suspending paste or carrier medium must be sufficiently viscous to maintain a smooth suspension of the starch particles, but not so viscous as to interfere with the application of the adhesive to the paper board.
• the nature and proportion of dissolved solids in the carrier medium influences both pot life and the speed with which a given paper stock absorbs water from the applied adhesive.
• the water content of the adhesive affects adhesive properties. A small degree of water absorption from the adhesive to the paper is desirable in forming strong bonds between the paper plies. Absorption of water beyond that required to give good bonding is undesirable since it robs the adhesive of water needed to complete the gelatinization of the suspended starch upon heating in the corrugator and leads to inferior bonding.
• the cold water insoluble polyvinyl alcohol (PVOH), a polyhydroxy polymer having a polymethylene backbone with pendent hydroxy groups, is a synthetic resin that removes better than 98.5% of the acetyl group and in certain grades of polymer better than 99% of the acetyl groups. It is produced by the hydrolysis of polyvinyl acetate. The theoretical monomer: ##STR1## does not exist. It is commonly available as a dry solid and is available in granular or powdered form. PVOH grades include a "super" hydrolyzed form (99.3% plus removal of the acetate group), and a fully hydrolyzed form (99%+removal of the acetate group).
• the properties of the resins vary according to the molecular weight of the parent polymer and the degree of hydrolysis.
• Polyvinyl alcohols are commonly produced in nominal number average molecular weights that range from about 20,000 to 100,000. Commonly the molecular weight of commercial polyvinyl alcohol grades is reflected in the viscosity of a 4 wt-% solution measured in centipoise (cP) at 20° C. with a Brookfield viscometer. The viscosity of a 4% solution can range from about 5 to about 65 cP. Variation in film flexibility, water sensitivity, ease of solvation, viscosity, block resistance, adhesive strength, dispersing power can all be varied by adjusting molecular weight or degree of hydrolysis.
• Solutions of polyvinyl alcohol in water can be made with large quantities of lower alcoholic cosolvents and salt cosolutes.
• Polyvinyl alcohols can react with aldehydes to form acetals, can be reacted with acrylonitrile to form cyanoethyl groups, and can be reacted with ethylene or propylene oxide to form hydroxy alkylene groups.
• Polyvinyl alcohols can be readily crosslinked and can be borated to effect gellation.
• Polyvinyl alcohol is made by first forming poly-vinyl acetate or a vinyl acetate containing copolymers such as an ethylene vinyl acetate copolymers and removing the acetate groups using a base catalyzed alkanolysis.
• the production of polyvinyl acetate or a vinyl acetate copolymer can be done by conventional processes which controls the ultimate molecular weight. Catalyst selection temperatures, solvent selection and chain transfer agents can be used by persons skilled in the art to control molecular weight.
• the degree of hydrolysis is controlled by preventing the completion of the alkanolysis reaction.
• Polyvinyl alcohol is made in the United States by Air Products & Chemicals, Inc. under the tradename VINOL®, by duPont under the trade name ELVANOL®, and by Monsanto under the trade name GELVITOL®.
• the preferred polyvinyl alcohol compositions for use in this invention comprise polyvinyl alcohol made from a homopolymer or interpolymer of vinyl acetate that is fully hydrolyzed, i.e. greater than about 98.5 to 99% of the hydroxyl groups are free of acetate or super hydrolyzed, greater than 99.3% of hydrolysis.
• the preferred fully hydrolyzed polyvinyl alcohol is available in low, medium or high molecular weight variations characterized by the Brookfield viscosity of a 4 wt-% aqueous solution at 20 degrees.
• a high molecular weight composition (MW 106,000 to 110,000) has a viscosity of about 35-60 cP.
• the preferred polyvinyl alcohol compositions have a reduced particle size adapting the composition for rapid dissolution.
• the particle size of the most preferred polyvinyl alcohol is such that 99+% of the product will pass through a -80 mesh screen.
• the most preferred polyvinyl alcohol composition is made from a low to medium molecular weight homopolymer of vinyl acetate that is fully hydrolyzed.
• the use of higher molecular weight polymers are more likely to gel at higher concentrations.
• the starch based adhesives of this invention are commonly characterized as being either a carrier adhesive, a no carrier adhesive, or a carrier/no carrier adhesive.
• carrier adhesive implies the presence of a thin base of gelatinized starch in which ungelatinized or nonhydrated starch particles are emulsified or suspended.
• no carrier adhesive implies the substantial absence of gelatinized or hydrated starch in the adhesive emulsion.
• carrier/no carrier adhesive implies that the distinction between gelatinized starch and ungelatinized starch is not clear in the adhesive composition.
• carrier/no carrier adhesives are prepared in a way that a substantial amount of partly hydrated or partly gelatinized starch is formed.
• the starch used in both the carrier phase and suspended starch phase is a commodity chemical produced from a number of root, stem or fruit, plant sources.
• Starch is a high molecular weight polymeric carbohydrate polysaccharide, most commonly composed of six carbon monosaccharide units joined by alpha-glycan linkages having an approximate molecular formula of (C 6 H 10 O 5 ) n , wherein n equals 10 2 to 10 6 .
• Starch occurs naturally in the form of white granules and comprise linear and branched polysaccharide polymers.
• Starch is commonly manufactured by first soaking and grinding the plant starch source, and separating the starch from waste matter. The starch is commonly reslurried and processed into a finished dried starch product.
• starch often has the form of a pearl starch, powdered starch, high amylose starch, precooked or gelatinized starch, etc.
• pearl starch is used in making both the carrier phase and the particulate starch suspended in the carrier.
• novel adhesive compositions of the invention contain a strong base which promotes the production of crosslinking species from the resin and acts to cure the adhesive.
• a strong base can be used, however preferred bases are alkali metal hydroxides.
• the most preferred strong bases include sodium and potassium hydroxide.
• the strong base also lowers the gel point of the starch, which increases the rate of hydration of the starch during curing of the glue line.
• boric acid compounds such as boron oxides, boric acids and borates
• the boric acid compound increases the tackiness, viscosity, and cohesive strength of the adhesive.
• a gel structure forms between the hydroxyl group of the polysaccharide, the basic acid compound and the PVOH.
• the borax buffers the caustic nature of the base used in the adhesive stabilizing the adhesive to the hydrolytic effect of the base.
• Resins that can be used in the novel adhesive compositions of this invention include resins that upon heating in basic media generate crosslinking species that react with and crosslink the hydroxyls in adjacent starch molecules.
• the crosslinking reagent tends to reduce the hydrophilic nature and the water solubility of the starch molecules by effectively removing the availability of hydroxyl groups to water and by introducing aliphatic alkylene-type crosslinking moieties.
• a preferred class of crosslinking resins comprise well known condensation products of the reaction of a ketone and an aldehyde compound. These resins are characterized as a polyether polymer but can contain a variety of other monomers such as urea, melamine, etc. In the presence of heat and base, they commonly decompose to produce species that effectively crosslink the starch molecules.
• Preferred resins are acetone-formaldehyde resins, acetone-urea-formaldehyde resins, acetone-melamine-formaldehyde resins comprising 15 to 30 wt-% acetone, about 5 to 50 wt-% formaldehyde and 0 to 15 wt-% of third monomer.
• One example of the preferred crosslinking resin embodiment of this invention comprises the Ketack, series of resins manufactured by American Cyanamide.
• wax is used very broadly and is applied to a wide variety of materials.
• the materials can have properties resembling certain well known waxes or can be used to provide physical properties similar to those associated with well known properties of wax such as sealing, polishing, candle making, etc.
• Many waxy substances have been found in nature and have been known to be useful for many years.
• waxes include substances that are natural products. Chemically natural waxes are esters of fatty acids and monohydric fatty alcohols. Physically waxes are water repellant solids having a useful degree of plastic character. However, modern waxes include various synthetic substances that can replace natural waxes in many preparations.
• the composition of natural waxes generally comprise an ester of a saturated fatty acid and a long chain monohydric alcohol. Long chain fatty acids often include acids having greater than 16 carbon atoms and most commonly about 26 carbon atoms. The aliphatic monohydric alcohol commonly has at least 14 and can range as high as 36 carbon atoms. Petroleum, mineral or other synthetic waxes often consist of saturated hydrocarbons having aliphatic or open chain structures with relatively low branching or side chains.
• waxes for the water resistant corrugated board adhesive are waxes such as petroleum waxes, candelilla wax, beeswax, etc.
• Particularly preferred waxes are the petroleum waxes such as microcrystalline waxes, slack waxes and paraffin waxes.
• the adhesive can contain from about 5 to 75 parts of starch and about 0.1 to about 10 parts of base per 100 parts of the adhesive composition.
• the carrier phase comprises about 1 to 25 parts of starch and the ungelatinized phase comprises 5 to 50 parts of starch per each 100 parts o adhesive.
• the adhesive can contain about 0.1 to 5 parts of boric acid per each 100 parts of water and optionally about 0.1 to 5 parts of basically reacting crosslinking resin per 100 parts of water and about 0.1 to 5 parts of wax in an emulsion form per each 100 parts of water.
• the fast setting adhesive of this invention contain about 0.01 to 2.0 parts of polyvinyl alcohol per each 100 parts of adhesive.
• the adhesive contains about 0.1 to 1.5 parts of polyvinyl alcohol and most preferably for reasons of rapid set and compatibility with the adhesive components about 0.25 to 1.25 parts of polyvinyl alcohol per 100 parts of adhesive.
• the ratio of polyvinyl alcohol to boric acid is important in the invention since the interaction between polyvinyl alcohol and boric acid can cause substantial gelling problems and the manufacture of the adhesive.
• VINOL 107 a fully hydrolyzed low molecular weight polyvinyl alcohol
• a stock solution of sodium hydroxide, 5-mol borax and water was prepared which is representative of a corrugating adhesive mixture without the starch.
• the table of data shows that the amount of the high molecular weight fully hydrolyzed PVOH places in solution must be carefully controlled to avoid gellation and compatibility problems.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Machines For Manufacturing Corrugated Board In Mechanical Paper-Making Processes (AREA)

Priority Applications (9)

Applications Claiming Priority (1)

Related Child Applications (1)

Publications (1)

Family

ID=25388024

Family Applications (1)

Country Status (8)

Cited By (13)

Families Citing this family (5)

Citations (4)

• 1986
  • 1986-07-15 US US06/885,933 patent/US4826719A/en not_active Expired - Lifetime
• 1987
  • 1987-07-13 CA CA000541886A patent/CA1337611C/en not_active Expired - Lifetime
  • 1987-07-15 JP JP62175008A patent/JPS6392677A/ja active Pending
  • 1987-07-15 AT AT87306252T patent/ATE73838T1/de not_active IP Right Cessation
  • 1987-07-15 ES ES198787306252T patent/ES2030727T3/es not_active Expired - Lifetime
  • 1987-07-15 DE DE8787306252T patent/DE3777479D1/de not_active Expired - Lifetime
  • 1987-07-15 EP EP87306252A patent/EP0253643B1/de not_active Expired - Lifetime
• 1992
  • 1992-05-26 GR GR920401035T patent/GR3004701T3/el unknown

Patent Citations (5)

Also Published As

Similar Documents

Legal Events